As a personal observation, I was always told that daito ryu and itto ryu were closely related. I actually think daito ryu and tatsumi ryu have a lot of similarities (to my eyes). However, I have never trained in a sword ryu. There is enough to learn about grabbing before moving on to stabbing

Sokaku Takeda was actually licensed in Ono-ha Itto ryu, and there is a line of Itto ryu that is transmitted through some Daito ryu groups which is not, I think, recognized by the Soke of Ono-ha Itto ryu. This is a stronger connection than the one to Jikishinkage ryu. But Jikishinkage ryu is somewhat unique in that it has preserved a vastly stronger emphasis on building power and stability before teaching sophisticated bladework than other existing schools. I think that is why you see the suburi practiced in Daito ryu today...it is a respected way to develop power.

I haven't seen enough of Tatsumi ryu to notice any similarities. There are plenty of things in koryu that resemble other things in koryu with which they have absolutely no connection, in my experience, so beware.